There are heat exchangers known in the related art achieved with a heat exchange medium flowing through at least four passes and having a tank provided as a component separate from tubes, in which any defective bonding of a partitioning portion can be detected with ease (see, for instance, Japanese Unexamined Patent Publication No. H10-19490).
In addition, there is a structure known in the related art adopted in a heat exchanger achieved with a heat exchange medium flowing through at least four passes and having a tank provided as a component separate from tubes, in which two chambers are formed side-by-side along the direction of the air flow by partitioning the tank with a partitioning wall ranging along the direction in which the tubes are layered and each chamber is further divided into sub-chambers with a partition plate inserted through a slit formed at the side face of the tank (see, for instance, Japanese Unexamined Patent Publication No. 2001-74388).
However, the structure of the heat exchanger disclosed in Japanese Unexamined Patent Publication No. H10-19490 needs to be adopted in conjunction with a partitioning portion ranging along the lengthwise direction relative to the tank and formed as an integrated part of the tank through roll forming, and cannot be directly adopted in a heat exchanger in which a partition plate is utilized to form a plurality of sub-chambers by dividing each chamber into a plurality of partitioned chambers along the direction of the air flow, as in the present invention.
The heat exchanger disclosed in Japanese Unexamined Patent Publication No. 2001-74388 poses a problem in that since a single slit extending substantially over the full width of the tank along the air flow direction needs to be formed, the strength of the tank is greatly compromised. In addition, since no slit is formed at the face of the tank at which tube insertion holes are formed, there arises another problem in that a bypass leakage of the heat exchange medium resulting from defective bonding of the partition plate and the tank occurring at this face cannot be detected as a pneumatic leak.
Accordingly, an object of the present invention is to provide a tank for a heat exchanger having a partition plate inserted at the tank through a slit formed at a side face of the tank in order to further partition each of chambers defined with a partitioning wall ranging along the direction in which tubes are layered into sub-chambers formed side-by-side along the layering direction, which assures that bypass leakage of the heat exchange medium is prevented from occurring between the sub-chambers with a high degree of reliability and maintains a required level of strength in the tank even with the slits formed thereat.